Cu(x)O-Modified Nanoporous Cu Foil as a Self-Supporting Electrode for Supercapacitor and Oxygen Evolution Reaction

Designing and modifying nanoporous metal foils to make them suitable for supercapacitor and catalysis is significant but challenging. In this work, Cu(x)O nanoflakes have been successfully in situ grown on nanoporous Cu foil via a facile electrooxidation method. A Ga-assisted surface Ga-Cu alloying–dealloying is adopted to realize the formation of a nanoporous Cu layer on the flexible Cu foil. The following electrooxidation, at a constant potential, modifies the nanoporous Cu layer with Cu(x)O nanoflakes. The optimum Cu(x)O/Cu electrode (O-Cu-2h) delivers the maximum areal capacitance of 0.745 F cm(−2) (410.27 F g(−1)) at 0.2 mA cm(−2) and maintains 94.71% of the capacitance after 12,000 cycles. The supercapacitor consisted of the O-Cu-2h as the positive electrode and activated carbon as the negative electrode has an energy density of 24.20 Wh kg(−1) and power density of 0.65 kW kg(−1). The potential of using the electrode as oxygen evolution reaction catalysts is also investigated. The overpotential of O-Cu-2h at 10 mA cm(−2) is 394 mV; however, the long-term stability still needs further improvement.